There are many mechanical machining procedures which employ grinding tools. In particular, in the field of gear tooth processing grinding tools are employed which may be dressed. There are, for instance, grinding discs which are almost saucer-shaped, cup-shaped or conical. These grinding tools are typically covered with an abrasive material that is especially suited for dressing.
In addition to the grinding tool there is often provided a dressing tool in a grinding machine, which may be employed for dressing the grinding tool if needed. Modern grinding machines typically comprise a dressing tool driven so as to rotate and which are contour controlled for an automated definition and for the dressing of the grinding tool.
If, for example, the grinding of a toothing is concerned, the working surfaces of the grinding tool have to be brought back into the desired shape (called profiling) after a certain period of time in order to guarantee a sufficient quality of the toothing.
It is a precondition for dressing by means of dressing tools that a relative dressing (grinding) movement may occur between the dressing tool and the grinding tool. The dressing tool may rotate in the same direction or in the opposite as the grinding tool. For rotating dressing tools, the velocity ratio between the grinding tool and the dressing tool is one of the parameters that may influence the dressing result.
The form and profile dressing procedures are subject to many factors that may influence the dressing of the grinding tool considerably.
Investigations have revealed that, when grinding a work piece after an interrupt of a production process, inaccuracies may result. Detailed analysis may lead to the conclusion that these inaccuracies are caused by temperature-induced variations of the grinding machine. A grinding machine in its cooled-down state, for example, has a minimum different relative position of the grinding tool relative to the dressing tool and/or to the work piece than a continuously operating grinding machine, which may have a higher intrinsic temperature. Such an altered relative position caused by the temperature may have an impact on the accuracy of the dressing. That is, the grinding tool may have a slightly changed geometry as compared to the nominal value.
It is well known that a contouring machine might be equipped with a tactile coordinate sensor, e.g., in order to measure the work piece during processing or during processing breaks. Such a tactile coordinate sensor, however, is neither suitable for measuring the dressing tool nor for measuring the grinding tool. This is because the dressing tool is typically covered with poly-crystal or natural diamond or some other hard material. When contacting the dressing tool, the ruby-probe of a tactile coordinate sensor could get destroyed quickly.